video analysis
rallain | November 18, 2008Big trucks are not as popular as they used to be, but gas prices are going down so maybe this commercial for the ford F-150 will start showing up again:
They say its a real demonstration, but it has seemed odd to me. (they also say this is a professional driver on a closed course and don't try this at home - damn! I was SO going to do that this weekend). Here is my analysis:
Here is the important data I have gathered from the Internets.
The truck (a Ford F-150) stops a plane C-123 Provider
The curb weight of the F-150 is around 5,000 lbs - depending on options and stuff.
The empty weight of…
rallain | November 14, 2008Here is a video of a guy jumping 35 feet into a pool of water only 1 foot deep.
UPDATE: Apparently, that video went away. Here is another version.
How does this work?
I don't think I even need to do a video analysis of this motion, all the important info is given. I will assume that air resistance did not play a signficant role (and that is a good assumption - or good enough - see this for example: motion of a falling tennis ball). So, here is the situation.
Part 1: guy falls 35 feet 5 inches (10.8 meters).
. Really an interesting show. There are many videos that I could see some analysis project for (too bad I am like 20 projects behind schedule - I think of things faster than I can do them). There is one problem though. It seems like all of the people on the show like to use physics terms, but they use them incorrectly. This DRIVES ME NUTS. You can't have "energy going this way". Energy is a scalar, not a vector. You can't have "force flowing through this". You can't "put…
rallain | October 28, 2008Here is what is cool about [Fantastic Contraption](http://fantasticcontraption.com/) - it's like a whole new world, a world ready for exploring. I am Newton, and I can see if this world follows the models that I propose.
In this post, I am going to explore the elastic nature of the "water-sticks". If you have played fantastic contraption, I am sure you noticed that the water-sticks are springy. How does these springy sticks work? Are they just like the springs we have in the real world? An excellent model for springs in the real world is Hooke's law. It says the force exerted by a…
rallain | October 26, 2008The fun part about exploring the physics of [Fantastic Contraption](http://fantasticcontraption.com/) is coming up with new setups to test ideas. Torque is not too difficult to set up. Here is what I did:
In this setup, I have a "turning ball" with a wood stick attached to the side. I increased the length of the stick until the ball does not turn. At this point, the torque from the gravitational force on the stick is equal to the torque from the ball. I can use [Tracker Video Analysis](http://www.…
rallain | October 23, 2008One of my students showed me this game, [Fantastic Contraption](http://fantasticcontraption.com/). The basic idea is to use a couple of different "machine" parts to build something that will move an object into a target area. Not a bad game. But what do I do when I look at a game? I think - hey! I wonder what kind of physics this "world" uses. This is very similar to [my analysis of the game Line Rider](http://scienceblogs.com/dotphysics/2008/09/the-physics-of-linerider/) except completely different.
Fantastic Contraption gives the unique opportunity to build whatever you want. This…
rallain | October 2, 2008I was recently re-watching a MythBusters episode and I found something I had wanted to explore previously (but accidentally deleted the episode). Here is a short clip from the "shooting fish in a barrel" episode:
Did you see what I found interesting? That big barrel of water left the floor from being hit by a bullet.
The question here is: Does a bullet have enough energy to increase the gravitational potential energy of the barrel to that height?
First, let me gather some data. From the episode, the Mythbusters were firing a 9mm pistol round into the barrel. I don't know much about…
rallain | September 14, 2008Can you believe it? Have you seen this video?
Are you thinking what I am thinking? WOW. How could these people not follow my rules for cool internet video. Once again, here they are:
1Keep the camera stationary. This way I don't have to keep moving the origin in the movie.
2Don't Zoom. Same reason, this video followed that rule.
3Include a clear and obvious calibration object. A meter stick would work, or even a Kobe Bryant (I can look up his height). Maybe it could be a Ford F-150 that has a known length. Something!
4Include the mass and height of all people involved.
5Use high…
rallain | September 14, 2008Friction in Line Rider
Is there friction in Line Rider? Does it function as physics would expect? To test this, I set up a simple track:
Basically, a slope with a flat part to start with and to end with. Let me show you something simple before further analysis:
This is the x-position vs. time for the line rider on the first horizontal portion of the track (before he or she goes down the incline). This shows the rider…
rallain | September 13, 2008There is no air resistance in line rider. Sorry to spoil the suspense.
To test for the presence of an air resistance force, a track was created that let the rider fall.
(note the markers on the side. These are used to keep track of how the origin is moving).
Below is the y position of the rider as a function of time:
In this situation, the rider falls about 100 meters. A quadratic line is fit to the data…
rallain | September 13, 2008Scale of the Line Rider
First, we assume that the line rider is on Earth and for low speeds will have a free-falling acceleration of 9.8 m/s2. Next, an arbitrary distance is selected. In this case the length of the sled is chosen to be 1 LU (Linerider Unit).
The goal will be to put the linerider in a free fall (where air resistance should be able to be ignored) and determine his (it could be a she, it is difficult to tell) acceleration in LU/s2. Then we can determine the conversion factor from LU/s2 to…
rallain | September 13, 2008Part I: Introduction
http://linerider.com is a flash "game" in which the user can create tracks. A rider is then allowed to slide down these tracks. If you have not played this, I recommend you DON'T play it. It is very addicting and can consume many hours of your time (hours you would otherwise spend on Digg or surfing needlessly).
In this short report, I will analyze the physics involved in line rider. An obvious question is "why not just ask the line rider programmer?". Well, that would not be too much fun. Would it? So, there is the first reason - its fun. The second reason is to give an…
rallain | September 6, 2008Here is the video in question:
Looks too incredible to be real for me. That is when I start to question things. Is this fake or not? To answer this, I took a clip that showed a person launching a grocery item over the isle. This was a good shot to look at because it was *mostly* perpendicular to the camera view. I then used [Tracker video analysis (free) tool](http://www.cabrillo.edu/~dbrown/tracker/) to get x-y-time data for the flying projectile grocery. The scale was difficult, so I just guessed that the guy on the left was 5 foot 10 inches. Here is the vertical position data for…